Union Carbide cellular silicones. Final report
FrancisWm. Smith · 1972
An improved base for cellular silicone materials was developed utilizing end-blocked polysiloxane gum, resulting better reproducibility of properties from lot to lot, better processing properties, and lower compression set values. Y-3260 and Y-3333 were manufactured on a production scale and found to be superior to standard cellular silicone materials with respect to reproducibility of the gum, base compound, and final cellular cushions. The new materials also possess good processibility, easily meeting dimensional tolerances over a long period of compound storage. The lower Williams Plasticity Test values show improved plastic flow and a reduction in the molding pressures required to make complicated shapes. These new cellular silicone compounds permit the manufacture of silicone rubber cushions which have the lowest compression set test values ever obtained. The new materials recovered all but 6 to 10 percent of the standard test deformation of 50 percent for 22 hours at 300/sup 0/F; compared to the 15 percent or more lost by the present product; this is a significant improvement and represents a loss of about 0.002 inches in thickness for a 0.060 inch thick cushion. The products gave better thickness uniformity in typical shaped parts at molding pressures of only one-third that used for standard material. Initial efforts in the area of easy processing and extended shelf life of cellular silicones indicate this goal could be achieved with a minimum of compromises utilizing the newly developed base. Recommendations for future investigation are included. (DLC)